IT MADE little difference whether Grafton murderer Andrew Mervyn Sumpton had consensual sex with the woman he later bashed, stabbed to death and burnt, Supreme Court Justice Peter Hamill said.

Sumpton faced court in Sydney on Friday for his first sentence hearing after being found guilty of murdering Michelle Roberts, 47, in her South Grafton home in May 2012.

The thin, grey-haired killer scribbled notes in the dock while the court heard how he went back to Ms Roberts' home after a night of heavy drinking and caved her face in, stabbed her 18 times in the chest and abdomen and six times in the upper thighs and genitals before lighting her body and house on fire.

Crown Prosecutor Jeffery McLennan told the court new evidence would be submitted before a sentence was handed down, including the disclosure of Sumpton's 1996 conviction for indecent treatment of a child under the age of 12 in Queensland.

He also said two witnesses may be called to give evidence about Sumpton's "bad character".

Defence barrister Mark Dennis said he planned to tender psychiatric and pain management reports that would shed light on the "hardship" Sumpton could face in jail.

Justice Hamill agreed there was a sexual element to the "brutal killing", but said determining precisely what it was "borders on speculation".

Mr McLennan posed several theories about what triggered Sumpton's "explosion of violence" in trying to determine if an aggravating feature existed, including his victim's possible reaction to Sumpton's "sexual dysfunction" or her rejection of his advances.

"I just think we are very much in the realms of... we don't know what happened in that room," Justice Hamill responded.